Because electrostatic precipitators of this type are operated under high pressures of around 3 to 30 bars and at high temperatures of about 300.degree. to 1200.degree. C., structural problems and problems with materials are encountered. Satisfactory solutions to these problems have not been made apparent prior to our work in this field.
For instance, the precipitator housings at least of industrial electrostatic precipitators must be circular in cross-section for reasons of strength, and it is desired much more than in other electrostatic precipitators to utilize the gas-flow area as fully as possible for the installation of corona discharge and collecting electrodes. For this reason, the precipitator housing is upwardly inclined at such an angle that the collected dust can be automatically discharged by gravity.
For this purpose the flow behavior of the dust under the operating conditions must be known. Such an arrangement will eliminate the need for installed dust conveyors which anyway would be operative only with restrictions in such precipitators.
The shape of the precipitator housing, its upwardly inclined position and the high pressures and temperatures necessitate special designs of the collecting and corona-discharge electrodes. The corona discharge electrodes must be suspended so as to be electrically insulated from the housing and must be spaced equal distances apart from the collecting electrodes everywhere so that the electrostatic field which is built up will result in a most effective collection of dust.
For this purpose it is essential to stress mechanically the corona-discharge electrodes, which have only a small cross section to enable them to satisfy their electrical functions. Whereas only the weight of the collector electrodes must be considered in their design, internal mechanical stresses must be allowed for in the design of corona-discharge electrode systems.
This gives rise to additional difficulties because the material from which such electrodes are made has only a relatively low strength at the high operating temperatures.